Which orbital notation represents an atom of beryllium in
the ground state?

Beryllium is the fourth element with a total of 4 electrons. In writing the electron configuration for beryllium the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the remaining 2 electrons for Be go in the 2s orbital. Therefore the Be electron configuration will be 1s22s2.

Explanation:

4d^55s^1 ( third choice)

answermeridional ;